Photochemical synthesis of 2-substituted benzothiazoles

The photochemical reaction of 1 -indolethiocarbanilides 1 , di- and tri-substituted thioureas 3–5 and 4,4 -di-methyl-2,6-dioxothiocyclohexanecarboxanilides 9 affording the respective benzothiazoles are described.     

Mass-spectrometric study of adamantane derivatives

Conclusions The characteristic features of the mass spectra of a number of monofunctional alkyladamantanes, substituted in junction points, were found.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1028–1030, May, 1972.     

Mass-spectrometric study of 4-azaphenanthrene derivatives

The mass spectra of 15 compounds of the 4-azaphenanthrene series and their deutero analogs with bulky R substituents (R=-CCPh, -CH=CHPh, CHBr-CHBrPh,-CH=CHC₆H₄OCH₃-p, -COOH, -COOC₂H₅, and -CONHNH₂) in the ortho position relative to the nitrogen atom were studied. An intense [M-H]⁺ ion peak, the appearance of which is evidently due to a process involving cyclization of the carbon atom of the side chain with the nitrogen atom, is formed in the fragmentation of the styryl derivatives. The fragmentation of the compounds with a methyl group in the ortho position relative to the styryl grouping is accompanied by the formation of an intense [M-Ph]⁺ ion peak. An ortho effect of the carboxyl and carbethoxy groups adjacent to the methyl substituent is observed in the mass spectra of the investigated compounds. The data obtained make it possible to establish the structures of bulky substituents in the ortho position relative to the ring nitrogen atom and the position of the methyl group in the pyridine ring of monomethylated azaphenahthrenes.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 659–665, May, 1979.     

Mass-spectrometric study of 2- and 4-thiobarbituric acid derivatives

The mass spectra of 2- and 4-thiobarbituric acids and some of their close analogs at ionizing voltages of 70 and 14 eV are compared. Qualitative and quantitative differences in the behavior of these compounds under the influence of electron impact were established. It is shown that the position of the thione group in the ring and the tautomeric transformations have a substantial effect on the character of the fragmentation of the investigated compounds. The established fragmentation principles make it possible to distinguish the structural isomers in a series of 2- and 4-thiobarbituric acids from their mass spectra.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 529–535, April, 1976.     

Synthesis of 2- and 2,5-substituted benzoxazoles and benzothiazoles

A number of 2- and 2,5-perfluoroalkyl and perfluoroalkylether substituted benzoxazoles and benzothiazoles have been prepared. Their relative hydrolytic stability has been examined. In all cases the benzothiazoles were more stable that the benzoxazoles. Substituents in the 2-position offering steric hindrance improve hydrolytic stability.     

Liquid-phase synthesis of 2-substituted benzimidazoles, benzoxazoles and benzothiazoles

A novel acid fluoride for use in the liquid-phase synthesis of substituted benzimidazoles, benzoxazoles and benzothiazoles was developed. Its synthetic utility is exemplified by a structurally diverse set of aromatic heterocycles. Final cleavage is achieved by treatment with sodium methoxide in methanol for 12 h. The corresponding benzimidazoles, benzoxazoles and benzothiazoles were obtained in good isolated yields (22-62%, four steps).     

Eco-friendly synthesis of 2-substituted benzothiazoles catalyzed by silica sulfuric acid

2-Substituted benzothiazoles have been synthesized via one-pot reaction from aromatic aldehydes and o-aminothiophenol catalyzed by silica sulfuric acid in absolute methanol at room temperature. The remarkable advantages offered by this method are an environmentally friendly and reusable catalyst, a simple procedure, mild conditions, short reaction times, and good to excellent yields of products.     

Mass-spectrometric study of some derivatives of furo- and dihydrofurocoumarins

Summary The mass spectra of eight compounds beloning to the class of linear furo- and dihydrofurocoumarins have been studied. A scheme of the fragmentation of these substances under the action of electron impact has been proposed. It has been shown that the mass-spectrometric method permits acyl derivatives of oreoselone to be distinguished reliably from acyl derivatives of dihydrooreoselol and the latter series of substances from derivatives isomeric with them belonging to the class of dihydrofuro- and dihydropyranocoumarins.M. V. Lomonsov Moscow State University. All-Union Scientific-Research Institute of Medicinal Plants. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 560–568, September–October, 1974.     

Mass-spectrometric study of the ring-chain tautomerism OF S- and N-Acylalkyl-2-mercaptobenzimidazole derivatives

The mass spectra of a number of S- and N-acylalkyl derivatives of 2-mercaptobenzimidazole were studied in order to investigate the ring-chain tautomerism of compounds of this group. It is shown that the fragmentation of the investigated compounds takes place from the open form of the molecular ion. The data obtained in this study are compared with the results of studies of the tautomeric equilibria in very dilute solutions. The principal fragmentation regularities were established.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 676–680, May, 1976.     

Mass-spectrometric study of phenothiasilines and of their derivatives and analogs

Conclusions A study was made of some phenothiasiline derivatives and analogs and the main paths of their fragmentation were established.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1619–1622, July, 1981.     

Mass-spectrometric study of adamantane derivatives (diadamantyls and diadamantylethanes)

Conclusions Characteristic differences were found to exist between the mass spectra of the isomeric compounds of the diadamantyl and diadamantylethane series.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 439–414, February, 1971.     

Mass-spectrometric study of the sesquiterpene lactone grossmisin and its derivatives

Summary The dissociative ionization of grossmisin [O–D]grossmisin, and two of its derivatives have been studied. The appearance of the main fragments in the mass spectrum of grossmisin is due to the elimination by the M⁺ ion of H₂O and CO molecules and CH₃ and OH radicals in various sequences. The hypothesis has been put forward that in the splitting off of a CH₃COOH molecule by the M^+° ion of acetylgrossmisin a rearrangement of the lactone ring takes place with its reclosure at the C₆ carbon atom of the seven-membered ring.M. V. Lomonosov Moscow State University. Patrice Lumumba International Friendship University, Moscow. All-Union Scientific-Research Institute of Medicinal Plants, Moscow. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 344–349, May–June, 1977.     

Mass-spectrometric study of the sesquiterpene lactone germanin-A and its derivatives

Summary The mass spectra of the sesquiterpene lactone germanin-A and 11 of its derivatives and deuterium analogs have been studied. A scheme has been put forward for the decomposition of germanin-A under the action of electron impact. It has been established that the elimination of a molecule of acid from position 8 in the dissociative ionization of germanin-A and of tetrahydrogermanin-A involves the hydrogen atom of the carboxy group present in position 10 of the sesquiterpene ring. On this basis, a suggested conformation of the germanin-A molecule has been put forward.M. V. Lomonosov Moscow State University. All-Union Scientific-Research Institute of Medicinal Plants, Moscow. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 337–345, May–June, 1978.     

Hexafluorosilicates of 2-substituted anilinium derivatives

The reaction of 45% fluorosilicic acid with methanol solutions of several 2-substituted anilines(L) gave hexafluorosilicates (LH)₂SiF₆. The products were studied by elemental analysis, IR spectroscopy, mass spectrometry, and thermogravimetry. The solubility and the hydrolytic stability of the salts were estimated. The structure of the complex [CH₃O(O)CC₆H₄NH₃]₂SiF₆ was determined by single-crystal X-ray diffraction. The ionic structure is composed of centrosymmetric SiF ₆ ^2? anions (the average Si-F bond length is 1.679(1) Å) and the [CH₃O(O)CC₆H₄NH₃]⁺ cations. The NH ₃ ⁺ group is the donor for the inner-cation H-bond with the carbonyl oxygen atom (NH···O), and for two ion-ion H-bonds (NH···F). The Si-F bond lengths correlate with the strengths of the H-bonds involving the corresponding fluorine atoms.     

Photochemical cyclization of thioformanilides by chloranil: An approach to 2-substituted benzothiazoles

2-Substituted benzothiazoles were efficiently synthesized by radical cyclization of thioformanilides induced by chloranil under irradiation in 1,2-dichloroethane and toluene at 80 °C. Hydrogen atom abstraction from thiobenzamide by triplet chloranil was the key step of the mechanism, as confirmed by LFP experiments. The methodology developed is simple and afforded the easily isolated products from moderate to good yield.